[PATCH net-next] ipv6: Add icmp_echo_ignore_anycast for ICMPv6

[PATCH net-next] ipv6: Add icmp_echo_ignore_anycast for ICMPv6

[Stephen Suryaputra]

In addition to icmp_echo_ignore_multicast, there is a need to also
prevent responding to pings to anycast addresses for security.

Signed-off-by: Stephen Suryaputra <ssuryaextr@gmail.com>
---
 Documentation/networking/ip-sysctl.txt |  5 +++++
 include/net/netns/ipv6.h               |  1 +
 net/ipv6/af_inet6.c                    |  1 +
 net/ipv6/icmp.c                        | 16 ++++++++++++++--
 4 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 55ea7def46be..bd029fc55ccb 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -1923,6 +1923,11 @@ echo_ignore_multicast - BOOLEAN
 	requests sent to it over the IPv6 protocol via multicast.
 	Default: 0
 
+echo_ignore_anycast - BOOLEAN
+	If set non-zero, then the kernel will ignore all ICMP ECHO
+	requests sent to it over the IPv6 protocol destined to anycast address.
+	Default: 0
+
 xfrm6_gc_thresh - INTEGER
 	The threshold at which we will start garbage collecting for IPv6
 	destination cache entries.  At twice this value the system will
diff --git a/include/net/netns/ipv6.h b/include/net/netns/ipv6.h
index e29aff15acc9..64e29b58bb5e 100644
--- a/include/net/netns/ipv6.h
+++ b/include/net/netns/ipv6.h
@@ -34,6 +34,7 @@ struct netns_sysctl_ipv6 {
 	int icmpv6_time;
 	int icmpv6_echo_ignore_all;
 	int icmpv6_echo_ignore_multicast;
+	int icmpv6_echo_ignore_anycast;
 	int anycast_src_echo_reply;
 	int ip_nonlocal_bind;
 	int fwmark_reflect;
diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index fdc117de849c..fa6b404cbd10 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -848,6 +848,7 @@ static int __net_init inet6_net_init(struct net *net)
 	net->ipv6.sysctl.icmpv6_time = 1*HZ;
 	net->ipv6.sysctl.icmpv6_echo_ignore_all = 0;
 	net->ipv6.sysctl.icmpv6_echo_ignore_multicast = 0;
+	net->ipv6.sysctl.icmpv6_echo_ignore_anycast = 0;
 	net->ipv6.sysctl.flowlabel_consistency = 1;
 	net->ipv6.sysctl.auto_flowlabels = IP6_DEFAULT_AUTO_FLOW_LABELS;
 	net->ipv6.sysctl.idgen_retries = 3;
diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
index 0907bcede5e5..cc14b9998941 100644
--- a/net/ipv6/icmp.c
+++ b/net/ipv6/icmp.c
@@ -683,6 +683,7 @@ static void icmpv6_echo_reply(struct sk_buff *skb)
 	struct dst_entry *dst;
 	struct ipcm6_cookie ipc6;
 	u32 mark = IP6_REPLY_MARK(net, skb->mark);
+	bool acast;
 
 	if (ipv6_addr_is_multicast(&ipv6_hdr(skb)->daddr) &&
 	    net->ipv6.sysctl.icmpv6_echo_ignore_multicast)
@@ -690,9 +691,12 @@ static void icmpv6_echo_reply(struct sk_buff *skb)
 
 	saddr = &ipv6_hdr(skb)->daddr;
 
+	acast = ipv6_anycast_destination(skb_dst(skb), saddr);
+	if (acast && net->ipv6.sysctl.icmpv6_echo_ignore_anycast)
+		return;
+
 	if (!ipv6_unicast_destination(skb) &&
-	    !(net->ipv6.sysctl.anycast_src_echo_reply &&
-	      ipv6_anycast_destination(skb_dst(skb), saddr)))
+	    !(net->ipv6.sysctl.anycast_src_echo_reply && acast))
 		saddr = NULL;
 
 	memcpy(&tmp_hdr, icmph, sizeof(tmp_hdr));
@@ -1126,6 +1130,13 @@ static struct ctl_table ipv6_icmp_table_template[] = {
 		.mode		= 0644,
 		.proc_handler = proc_dointvec,
 	},
+	{
+		.procname	= "echo_ignore_anycast",
+		.data		= &init_net.ipv6.sysctl.icmpv6_echo_ignore_anycast,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler = proc_dointvec,
+	},
 	{ },
 };
 
@@ -1141,6 +1152,7 @@ struct ctl_table * __net_init ipv6_icmp_sysctl_init(struct net *net)
 		table[0].data = &net->ipv6.sysctl.icmpv6_time;
 		table[1].data = &net->ipv6.sysctl.icmpv6_echo_ignore_all;
 		table[2].data = &net->ipv6.sysctl.icmpv6_echo_ignore_multicast;
+		table[3].data = &net->ipv6.sysctl.icmpv6_echo_ignore_anycast;
 	}
 	return table;
 }
-- 
2.17.1

Re: [PATCH net-next] ipv6: Add icmp_echo_ignore_anycast for ICMPv6

[David Miller]

From: Stephen Suryaputra <ssuryaextr@gmail.com>
Date: Wed, 20 Mar 2019 10:29:27 -0400

> In addition to icmp_echo_ignore_multicast, there is a need to also
> prevent responding to pings to anycast addresses for security.
> 
> Signed-off-by: Stephen Suryaputra <ssuryaextr@gmail.com>

Applied, thank you.